Lungs conducting zone and respiratory zone function
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conducting zone respiratory zone functions physiology
| Feature | Conducting zone | Respiratory zone |
|---|---|---|
| Extent | Nose to terminal bronchioles | Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli |
| Main function | Conducts air to and from alveoli | Gas exchange between air and blood |
| Gas exchange | No gas exchange, so it forms the anatomical dead space | O₂ diffuses into pulmonary capillary blood; CO₂ diffuses into alveoli |
| Other roles | Filters particles by mucus and cilia, warms and humidifies inspired air, and helps protect lower airways | Provides a very large, thin, moist surface for rapid diffusion; surfactant lowers alveolar surface tension and helps prevent collapse |
Conducting zone:
Air passes through the nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles. Its job is to prepare and transport air, not exchange gases. The mucociliary escalator traps and removes inhaled particles. In a typical adult, this anatomical dead space is about 150 mL.
Air passes through the nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles. Its job is to prepare and transport air, not exchange gases. The mucociliary escalator traps and removes inhaled particles. In a typical adult, this anatomical dead space is about 150 mL.
Respiratory zone:
Begins at the respiratory bronchioles, where alveoli first appear. It is the site of pulmonary gas exchange across the alveolar-capillary membrane.
Begins at the respiratory bronchioles, where alveoli first appear. It is the site of pulmonary gas exchange across the alveolar-capillary membrane.
Source: Costanzo Physiology, 7th Edition, “Airways” section. The NCBI overview of lung dead space also distinguishes conducting-airway anatomical dead space from the gas-exchanging respiratory zone.
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